Control system and method for stopping vehicle

ABSTRACT

Provided are a control system and method for stopping a vehicle, which reduce jerk when a vehicle controlled by an SCC system is stopped by the SCC system without a driver&#39;s manipulation. A desired target stop distance between a controlled vehicle and a front vehicle is set. Proposed is a formula for calculating a target acceleration in which a jerk is not caused when the target stop distance is maintained and then the controlled vehicle stops. By controlling the stop of the controlled vehicle according to the acceleration that has been calculated with the formula, the controlled vehicle is stopped without the occurrence of a jerk.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 10-2012-0054629, filed on May 23, 2012, the disclosureof which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a smart cruise control (SCC) systemthat automatically adjusts the speed of a controlled vehicle on thebasis of information, such as the relative distance and relative speedof an ambient vehicle which are sensed by a sensor of the controlledvehicle, and thus prevents a traffic accident, and in particular, to acontrol system and method for stopping a vehicle, which decrease orprevent jerks that are caused when a vehicle is stopped by SSC, and thusenable the vehicle to reduce a speed or stop smoothly.

BACKGROUND

An SCC system denotes a system that determines the forward conditions ofa controlled vehicle by using a radar, and manipulates the engine orbrake of the controlled vehicle depending on the conditions, therebymaintaining a vehicle speed without the manipulation of a driver andadjusting a distance between vehicles.

The SCC system operates in an area of 30 km/h or more, but, as the SCCsystem has a stop-and-go function, the SSC system needs to provide astop control function. However, when a vehicle is stopped by the SCCsystem, large jerks, such as a pitch motion and noise dive, are causeddue to discontinuity in which there is no backing. Furthermore, eventhough a related art controller having no over-shoot function is used,due to practical limitations such as the delay and inaccuracy of a brakeapparatus and the delay and error of a radar, it is difficult to preventthe above-described drawbacks.

Due to practical uncertainty, a related art stop-and-go controllercannot prevent a jerk which is caused when a vehicle stops in driving.In methods of reducing the occurrence of jerks, there is a method thatrealizes a soft-stop function by decreasing a brake pressure in a slightdeceleration. The method cannot decrease or prevent the occurrence ofjerks, and cannot be applied to a case in which a deceleration is highor middle. Therefore, the method cannot respond to all drivingconditions. Also, there is a method that selects an appropriateparameter and performs variable control depending on driving conditions,but the method cannot propose a detailed scheme and result.

At present, there is an experimental method that decreases jerks whichare caused when a vehicle is stopped by the SCC system, only in alimited condition, but there is no deductive method that removes thecause of a jerk and thus prevents the jerk from occurring when a vehiclestops. Therefore, due to a jerk that is caused when a vehicle stops,many vehicles using the SCC system cause fatigued and unpleasantfeelings to a driver, and thus, the salability of SCC vehiclesdecreases.

SUMMARY

Accordingly, the present disclosure provides a method that sets a targetstop distance and calculates a target acceleration (which enablessoft-stop over the target stop distance) with a logical formula when acontrolled vehicle is stopped by an SCC system depending on the drivingor stop of a front vehicle.

The present disclosure also provides a control system and method forstopping a vehicle, which control the stop of a vehicle with acalculated target acceleration, and thus prevent a jerk from occurringwhen the vehicle is stopped by the SCC system depending on variousconditions.

In one general aspect, a SCC system includes: a receiver receivingrelative distance information and relative speed information of anambient vehicle and speed information and acceleration information of acontrolled vehicle which are sensed by a sensor of the controlledvehicle; a stop control activator generating a stop control activationsignal when a front vehicle is determined to be in a stop state whilethe controlled vehicle is driving, on the basis of at least one of aplurality of the received information; and a controller setting one of aplurality of predetermined stop distance candidates as a target stopdistance when the stop control activation signal is received, checkingwhether there is a design variable range that enables soft-stop over theset target stop distance on the basis of the information received by thereceiver, and calculating a target acceleration by using the target stopdistance and a design variable determined according to the checkedresult.

The controller may check whether the controlled vehicle is capable ofstopping before reaching the target stop distance, whether an absolutevalue of the target acceleration to be calculated with the designvariable and a practical acceleration in stop control exceed anallowable acceleration of the controlled vehicle, and whether the targetacceleration is capable of being estimated with a reaction speed of abrake apparatus, and determine the design variable. Furthermore, whenthere is a design variable range, the design variable may be determinedas an intermediate value within the design variable range, and whenthere is no design variable that satisfies the range, the designvariable may be determined as a maximum value of a plurality of boundaryvalues with the design variable range.

The controller may calculate a speed gain and a distance gain with thedetermined design variable, and more specifically, the controller maycalculate the speed gain and the distance gain by using at least one ofthe determined design variable and a time for which the controlledvehicle reaches a location of the front vehicle at a current speed.Furthermore, the controller may calculate the target acceleration withthe calculated speed gain and distance gain and the target stopdistance, thereby controlling the stop of the controlled vehicle.

In another general aspect, a SCC method includes: generating a stopcontrol activation signal when it is checked that an ambient vehicle isa stop state and a controlled vehicle is in a driving state, on thebasis of relative speed information of the ambient vehicle and speedinformation of the controlled vehicle which are sensed by a sensor ofthe controlled vehicle; setting one of a plurality of predetermined stopdistance candidates as a target stop distance when the stop controlactivation signal is received; checking whether there is a designvariable range that enables soft-stop of the controlled vehicle over theset target stop distance; calculating a speed gain and a distance gainwith an intermediate value within the design variable range when it ischecked that there is the design variable range; calculating a targetacceleration with the calculated speed gain and distance gain and thetarget stop distance; and transferring the target acceleration to adriving apparatus to control stop of the controlled vehicle.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a control system for stopping avehicle according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating in detail a process in a controller ofthe control system for stopping a vehicle according to an embodiment ofthe present invention.

FIG. 3 is a diagram showing an application example of the control systemfor stopping a vehicle according to an embodiment of the presentinvention.

FIG. 4 is a block diagram illustrating a control method for stopping avehicle according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The advantages, features and aspects of the present invention willbecome apparent from the following description of the embodiments withreference to the accompanying drawings, which is set forth hereinafter.The present invention may, however, be embodied in different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the presentinvention to those skilled in the art.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Hereinafter, exemplary embodiments will be described in detail withreference to the accompanying drawings.

FIG. 1 is a block diagram illustrating a structure of a control systemfor stopping a vehicle according to an embodiment of the presentinvention.

A sensor 110 or radar mounted on a controlled vehicle senses therelative distance and relative speed of an ambient vehicle (for example,a front vehicle) near the controlled vehicle, and transmits sensinginformation, including the sensed distance and speed signals, to avehicle stop control system 100. The sensing information may betransmitted through wired or wireless communication. The vehicle stopcontrol system 100 receives the sensing information and information onthe speed and acceleration of the controlled vehicle.

The vehicle stop control system 100 includes a stop control activator101, a receiver 102, and a controller 103. The receiver 102 receivesinformation on an ambient vehicle and information on the speed andacceleration of the controlled vehicle from the sensor 110 or radar ofthe controlled vehicle. The receiver 102 transfers the receivedinformation to the stop control activator 101 and the controller 103.

The stop control activator 101 determines whether the ambient vehicle isin a stop state on the basis of the relative speed information of theambient vehicle and the speed information of the controlled vehicle thatare inputted from the receiver 102. Furthermore, the stop controlactivator 101 determines whether the controlled vehicle is in a stopstate or a driving state, on the basis of the speed information andacceleration information of the controlled vehicle. In this case, whenthe speed of the controlled vehicle is higher than or equal to a certainspeed or the absolute acceleration is higher than or equal to a certainlevel, the stop control activator 101 determines there to be in thedriving state. When the front vehicle is in the stop state and thecontrolled vehicle is driving, the stop control activator 101 generatesa stop control activation signal and transfers the stop controlactivation signal to the controller 103.

The controller 103 starts to control the stop of the controlled vehicleaccording to the stop control activation signal inputted from the stopcontrol activator 101. In an operation of calculating a targetacceleration, the controller 103 uses vehicle information inputted fromthe receiver 102.

The controller 103 sets a target stop distance “c_(i)” (where i is aninteger from zero to N, which is a natural number more than or equal toone) that is a desired interval between the front vehicle and thecontrolled vehicle which is stopped, for performing stop control. Thecontroller 103 selects one distance from among a plurality ofpredetermined stop distance candidates (for example, N+1 number ofdistance values in which a current distance between vehicles is themaximum distance, and the N+1 distance values are set by sequentiallydecreasing the maximum distance in units of a distance of 0.5 m), andsets the selected distance as the target stop distance. The controller103 determines whether there is the range of a design variable “w_(n)”that enables the soft-stop of the controlled vehicle, over the settarget stop distance. When the first-set target stop distance is assumedas c_(o), the controller 103 determines whether there is a designvariable that meets the following conditions.

$\begin{matrix}{w_{n} \geq \frac{- {\overset{.}{e}(O)}}{{e(O)} - c_{o}}} & (1) \\{w_{n} \geq \frac{{- {\overset{.}{e}(O)}} + \sqrt{{\overset{.}{e}(O)}^{2} + {a_{{ma}\; x}( {{e(O)} - c_{o}} )}}}{{e(O)} - c_{o}}} & (2) \\{w_{n} \leq \sqrt{\frac{{a_{{ma}\; x}} \cdot \exp^{2}}{{e(O)} - c_{o}}}} & (3) \\{w_{n}{\operatorname{<<}\frac{1}{\tau}}} & (4)\end{matrix}$

where ė(O) denotes a speed difference between the front vehicle and thecontrolled vehicle, e(O) denotes a distance between the front vehicleand the controlled vehicle, a_(max) denotes the maximum allowablenegative acceleration of the SCC system, exp denotes a natural constant,and τ denotes the reaction speed of a vehicle actuator.

To describe in more detail conditions for checking an area in whichthere is the design variable, the minimum design variable range thatdoes not exceed a predetermined candidate target stop distance inperforming stop control is considered. This is specifically expressed asEquation (1). When the minimum design variable range is greater thanzero, the following condition is considered.

A design variable range in which the currently calculated absolute valueof a target acceleration is within an allowable acceleration. This maybe specifically expressed as Equation (2). A design variable range,which does not exceed an allowable acceleration when stop control isbeing performed after the present, is considered. This may bespecifically expressed as Equation (3). A design variable range, whichhas a stop control speed sufficiently slower than the reaction speed ofa brake apparatus, is considered. This may be specifically expressed asEquation (1).

The above-described conditions have been considered for a case in whichthe front vehicle stops, the controlled vehicle is driving, and adistance to the front vehicle is greater than a candidate target stopdistance. When there is the design variable “w_(n)” that meets theabove-described condition, the controller 103 calculates a targetacceleration “a_(i)” by using a currently set target stop distance andan intermediate value of values that meet the design variable range.

However, when there is no design variable range, the controller 103selects another stop distance candidate from among the predeterminedstop distance candidates to set a target stop distance as a new value,and determines whether there is no design variable range. When there isno design variable range for all of the stop distance candidates, thecontroller 103 calculates the target acceleration by using the shortesttarget stop distance of the stop distance candidates and the maximumvalue of boundary values of a design variable for the shortest targetstop distance.

A method, in which the controller 103 calculates the targetacceleration, uses the design variable (which has been obtained throughthe above-described operation) and the target stop distance that hasbeen set in determining the design variable value, in which case thecontroller 103 first calculates an SCC speed gain “k_(v)” and an SCCdistance gain “k_(c)” by using the design variable. The SCC speed gainand the SCC distance gain may be calculated with one of the followingEquations (5) and (6).

k _(v) +T _(g) k _(c)=2w _(n) ,k _(c) =w _(n) ²  (5)

k _(v)=2w _(n) ,k _(c) =w _(n) ²  (6)

where T_(g) indicates a time interval (sec) of the SCC system, anddenotes a time for which the controlled vehicle reaches the stoppedfront vehicle when the controlled vehicle is continuously driving at acurrent speed.

The controller 103 calculates the SCC speed gain and the SCC distancegain with Equations (5) and (6), and then calculates a targetacceleration “a_(i)” in which the controlled vehicle is capable ofmaintaining a constant distance to the front vehicle and stopping.

a _(i) =k _(v) ė+k _(c)(e−c _(i))  (7)

where ė denotes the relative speed of an ambient vehicle, e denotes therelative distance of the ambient vehicle, and c_(i) denotes the targetstop distance that has been set in determining the design variable.

The controller 103 may calculate the target acceleration “a_(i)” inwhich the target stop distance “c_(i)” between the front vehicle and thecontrolled vehicle is maintained and soft-stop in which a jerk does notoccur is performed, through the above-described operation. Thecontroller 103 transmits the calculated target acceleration “a_(i)” to adriving apparatus 120, thereby allowing the controlled vehicle to bestopped.

FIG. 2 is a diagram illustrating in detail a process in a controller ofthe control system for stopping a vehicle according to an embodiment ofthe present invention.

The controller 130 receives information on the relative distance andrelative speed of the front vehicle and information on the speed andacceleration of the controlled vehicle, through the receiver 102. Whenthe controller 103 receives the stop control activation signal, thecontroller 103 selects the target stop distance from among thepredetermined stop distance candidates, and checks whether soft-stop ispossible over the target stop distance. When soft-stop is impossible,the controller 103 selects a new target stop distance from among thepredetermined stop distance candidates, and checks whether soft-stop ispossible over the new target stop distance.

When the target stop distance has been checked, the controller 103calculates a target acceleration that enables soft-stop, by using theinformation on the relative distance and relative speed of the frontvehicle and the target stop distance, and thus controls the controlledvehicle according to the target acceleration.

FIG. 3 shows a case in which a target stop distance is changed or thedesign variable “w_(n)” increases due to an external factor such as thata brake force becomes lower in practical driving. In [1] of FIG. 3,since there is a design variable “w_(n)” that enables soft-stop over acorresponding target stop distance of 5 m, the controller 103 selectsthe design variable “w_(n)” as an intermediate value of a boundary tocalculate the control gains “k_(v)” and “k_(c)” and the targetacceleration “a_(i)”, and transfers the calculated gains and targetacceleration to the driving apparatus 120. In [2] of FIG. 3, since thereis no design variable “w_(n)” that enables soft-stop over acorresponding target stop distance of 6.8 m, the controller 103 selectsanother candidate stop distance and checks whether there is a designvariable “w_(n)” that enables soft-stop.

FIG. 4 is a block diagram illustrating a control method for stopping avehicle in which a jerk is not caused by the control system for stoppinga vehicle according to an embodiment of the present invention.

When the stop state of a front vehicle and the driving state of acontrolled vehicle are checked on the basis of information on therelative speed of the front vehicle and the speed/accelerationinformation of the controlled vehicle and stop control is activated bythe control system for stopping a vehicle in operation S400, the controlsystem selects and sets a target stop distance from among a plurality ofpredetermined stop distances in operation S410, and determines whetherthere is a design variable range in which the target stop distance ismaintained between the front vehicle and the controlled vehicle andsoft-stop is capable of being performed in operation S420.

When there is no design variable range that satisfies a necessarycondition over the set target stop distance, the control system checkswhether there is a new stop distance candidate in operation S430. Whenthere is the new stop distance candidate, the control system newly setsa target stop distance in operation S440, and then again determineswhether there is a design variable range in operation S420.

On the other hand, when there is the design variable range thatsatisfies the necessary condition over the set target stop distance, thecontrol system calculates a speed gain and a distance gain with anintermediate value within the design variable range in operation S450.When there is no design variable range over all target stop distances,the control system calculates the speed gain and the distance gain withthe maximum value of boundary values that satisfy Equations (1) to (4)in operation S460.

The control system calculates a target acceleration in which thecontrolled vehicle is capable of stopping without the occurrence of ajerk, by using the calculated speed gain, distance gain, and target stopdistance in operation S470. The control system transmits the targetacceleration to a driving apparatus in operation S480, and thus controlsthe stop of the controlled vehicle without the occurrence of a jerk.

As described above, the present invention provides the method that setsa target stop distance and calculates a target acceleration (whichenables soft-stop over the target stop distance) with a logical formulawhen a controlled vehicle is stopped by an SCC system depending on thedriving or stop of a front vehicle. Also, the present invention providesthe control system and method for stopping a vehicle, which control thestop of a vehicle with a calculated target acceleration, and thusprevent a jerk from occurring when the vehicle is stopped by the SCCsystem depending on various conditions.

A number of exemplary embodiments have been described above.Nevertheless, it will be understood that various modifications may bemade. For example, suitable results may be achieved if the describedtechniques are performed in a different order and/or if components in adescribed system, architecture, device, or circuit are combined in adifferent manner and/or replaced or supplemented by other components ortheir equivalents. Accordingly, other implementations are within thescope of the following claims.

What is claimed is:
 1. A smart cruise control (SCC) system, comprising:a receiver receiving relative distance information and relative speedinformation of an ambient vehicle and speed information and accelerationinformation of a controlled vehicle which are sensed by a sensor of thecontrolled vehicle; a stop control activator generating a stop controlactivation signal when a front vehicle is determined to be in a stopstate while the controlled vehicle is driving, on the basis of at leastone of a plurality of the received information; and a controller settingone of a plurality of predetermined stop distance candidates as a targetstop distance when the stop control activation signal is received,checking whether there is a design variable range that enables soft-stopover the set target stop distance on the basis of the informationreceived by the receiver, and calculating a target acceleration by usingthe target stop distance and a design variable determined according tothe checked result.
 2. The SCC system of claim 1, wherein the controllerchecks whether the controlled vehicle is capable of stopping beforereaching the target stop distance, whether an absolute value of thetarget acceleration to be calculated with the design variable and apractical acceleration in stop control exceed an allowable accelerationof the controlled vehicle, and whether the target acceleration iscapable of being estimated with a reaction speed of a brake apparatus,and determines the design variable.
 3. The SCC system of claim 1,wherein the controller calculates a speed gain and a distance gain withthe determined design variable, and calculates the target accelerationwith the calculated speed gain and distance gain and the target stopdistance.
 4. The SCC system of claim 1, wherein when it is checked thatthere is a design variable range which enables soft-stop over the targetstop distance, the controller determines an intermediate value withinthe design variable range as a design variable, and calculates thetarget acceleration with the determined design variable and the targetstop distance.
 5. The SCC system of claim 1, wherein, when it is checkedthat there is no design variable range which enables soft-stop over thetarget stop distance, the controller sets one of the other predeterminedstop distance candidates as a new target stop distance to check whetherthere is a design variable range, and when there is no longerpredetermined stop distance candidate, the controller calculates thetarget acceleration with a shortest target stop distance of thecandidates and a maximum value of a plurality of boundary values of adesign variable for the shortest target stop distance.
 6. The SCC systemof claim 1, wherein the controller transfers the calculated targetacceleration to a driving apparatus to control stop of the controlledvehicle.
 7. The SCC system of claim 2, wherein the controller determinesthe design variable from among a plurality of values within a range thatmeets the following Equations,$w_{n} \geq \frac{- {\overset{.}{e}(O)}}{{e(O)} - c_{o}}$$w_{n} \geq \frac{{- {\overset{.}{e}(O)}} + \sqrt{{\overset{.}{e}(O)}^{2} + {a_{{ma}\; x}( {{e(O)} - c_{o}} )}}}{{e(O)} - c_{o}}$$w_{n} \leq \sqrt{\frac{{a_{{ma}\; x}} \cdot \exp^{2}}{{e(O)} - c_{o}}}$$w_{n}{\operatorname{<<}\; \frac{1}{\tau}}$ where ė(O) denotes a speeddifference between the front vehicle and the controlled vehicle, e(O)denotes a distance between the front vehicle and the controlled vehicle,a_(max) denotes the maximum allowable negative acceleration of the SCCsystem, exp denotes a natural constant, and τ denotes the reaction speedof a vehicle actuator.
 8. The SCC system of claim 3, wherein thecontroller calculates the speed gain and the distance gain by using atleast one of the determined design variable and a time for which thecontrolled vehicle reaches a location of the front vehicle at a currentspeed.
 9. The SCC system of claim 8, wherein the controller calculatesthe speed gain and the distance gain with the following Equation,k _(v) +T _(g) k _(c)=2w _(n) ,k _(c) =w _(n) ² where k_(v) denotes aspeed gain, T_(g) denotes a time interval, k_(c) denotes a distancegain, and w_(n) denotes a design variable.
 10. The SCC system of claim8, wherein the controller calculates the speed gain and the distancegain with the following Equation,k _(v)=2w _(n) ,k _(c) =w _(n) ² where k_(v) denotes a speed gain, k_(c)denotes a distance gain, and w_(n) denotes a design variable.
 11. TheSCC system of claim 9, wherein the controller calculates the targetacceleration with the following Equation,a _(i) =k _(v) ė+k _(c)(e−c _(i)) where a_(i) denotes a targetacceleration, k_(v) denotes a speed gain, ė denotes a relative speed ofan ambient vehicle, k_(c) denotes a distance gain, e denotes a relativedistance of the ambient vehicle, and c_(i) denotes a target stopdistance.
 12. The SCC system of claim 10, wherein the controllercalculates the target acceleration with the following Equation,a _(i) =k _(v) ė+k _(c)(e−c _(i)) where a_(i) denotes a targetacceleration, k_(v) denotes a speed gain, ė denotes a relative speed ofan ambient vehicle, k_(c) denotes a distance gain, e denotes a relativedistance of the ambient vehicle, and c_(i) denotes a target stopdistance.
 13. A smart cruise control (SCC) method, comprising:generating a stop control activation signal when it is checked that anambient vehicle is a stop state and a controlled vehicle is in a drivingstate, on the basis of relative speed information of the ambient vehicleand speed information of the controlled vehicle which are sensed by asensor of the controlled vehicle; setting one of a plurality ofpredetermined stop distance candidates as a target stop distance whenthe stop control activation signal is received; checking whether thereis a design variable range that enables soft-stop of the controlledvehicle over the set target stop distance; calculating a speed gain anda distance gain with an intermediate value within the design variablerange when it is checked that there is the design variable range;calculating a target acceleration with the calculated speed gain anddistance gain and the target stop distance; and transferring the targetacceleration to a driving apparatus to control stop of the controlledvehicle.
 14. The SCC method of claim 13, further comprising: setting oneof the other predetermined stop distance candidates as a new target stopdistance when it is checked that there is no design variable range; andcalculating the target acceleration with a shortest target stop distanceand a maximum value of a plurality of boundary values within a designvariable range for the shortest target stop distance, when there is nolonger predetermined stop distance candidate.